Energy Density of a Fuel (WJEC GCSE Chemistry)

Energy Released by Fuels

• We can experimentally determine the amount of energy released by a fuel 

• We do this using calorimetry

• The apparatus for this experiment is shown below  

Diagram to show the set up of calorimetry equipment

A lid is used to prevent heat loss

• The steps are: 

  1. Measure a fixed volume of water into a copper can

  2. Weigh the spirit burner containing  a fuel using a balance

  3. Measure the initial temperature of the water

  4. Burn the fuel and stir the water 

  5. Wait until the temperature has risen by approximately 20 ^oC and extinguish the flame

  6. Record the final temperature of the water and re-weigh the spirit burner

• To calculate the energy released by the fuel we can use the data obtained from the experiment above and the specific heat capacity of water 

• The specific heat capacity, c, is the energy needed to raise the temperature of 1 g of a substance by 1 °C

  • The specific heat capacity of water is 4.18 J/g/°C

• The heat energy change is calculated using:

Q = m x c x ΔT

• Q = the heat energy change, J

  • m = the mass of the substance being heated, g

  • c = the specific heat capacity, J/g/°C

  • ΔT = the temperature change, °C